Hydroplane hull



March 28, 1939. E, w EASTHOPE 2,151,958

HYDROPLANE HULL Filed Fe 1, 1957 1 II III] INVENTOR [RNEST Will/ANS [ASTHOPE ATTORNEY.

Patented Mar. 28, 1939 1 UNITED STATES PATENT OFFICE 6 Claims.

My invention relates to improvements in hydroplane hulls where frontal air pressure is relied upon to exert an upward lift under the hulls to reduce their draught and consequently reduce the skin friction produced by the water in contact with the hull.

The objects of the invention are to utilize the frontal air pressureto lift the hull and to provide means whereby the hull when lifted will maintain a substantially even longitudinal level, avoiding particularly the forward lift and subsequent pounding which is so prevalent in stepped hulls now in regular use. A further object is to provide means which will tend to lift the stern at relatively low speeds, such as when starting and getting up to speed and to retain the major portion of the bottom wall of the hull out of contact with the water, so that the air pressure developed from high speedforward movement may be retained substantially at a constant at the point of its escape at the stern of the boat.

The invention consists of a stepped hull having a relatively flat bottom sloping downwardly to the stern and one or more runners extending longitudinally of said bottom, which are inclined for a portion of their length in the same direction as the bottom but to a greater angle, as will be more fully described in the following specification and shown in the accompanying drawing, in which:

Fig. 1 is an elevational view of a typical hydroplane hull fitted with the invention.

Fig. 2 is a fractional transverse section taken on the line 22 of Figure 1.

Fig. 3 is a fractional transverse section taken on the line 3-3 of Figure 1.

Fig. 4 is a longitudinal view of one of the runners.

Fig. 5 is a sectional view of a modified arrangement of the runners.

In the drawing like characters of reference in- 50 step 3 to the rear step 4, which side boards are fitted to the sides of the hull and extend downwardly into the water to prevent escape of air compressed beneath the bottom 2 by frontal pressure at the bow, outwardly past the sides of the 55 hull. Secured preferably at the intersection of the side boards 6 and the bottom 2 of the hull are runners I which extend forwardly from the rear step 4 towards the perpendicular of the forward step. The major portion of the bottom wall 8 of the runners is parallel to that portion of the bot- 5 tom 2 which extends between the rear and forward steps or is inclined downwardly to the rear from the forward step as at 9, so as to present a planing surface to each runner which will tend to lift the bottom of the hull towards the stern out 10 of the water. The forward end of the runners is less in depth than the forward step as at M, so that no water drag can exist when the hull is travelling at such speed that the forward step is substantially lifted from the Water. The rear 15 end of each runner may be, if desired, at such an angle to the remainder of its bottom wall 8 as to be parallel to the water line shown as a dotted line vI I, when the hull is travelling at approximately maximum speed. 20

The underside of the forward end of each of the runners is preferably chamfered oif on one side as at l2, see Figure 3, to reduce weight and skin friction, or water drag when the hull is attaining speed. 25

In the modification shown in Figure 5, one or more runners 1 are extended longitudinally of the bottom wall, if one only is used it would be disposed equidistantly between the side boards 6, and if two are used they would be spaced at sub- 30 stantially equal distances from said side boards and from each other.

The effect obtained by the runners is as followsz-When the boat is getting under Way there is a relatively great hull area in contact with 35 the water causing skin friction, the water skin friction is reduced progressively as the hull lifts. As the bow 5 lifts, the frontal pressure increases due to increased frontal area-exposed and air is driven under the bottom imparting first a lift 40 at the bow which normally tends to increase as the speed increases, until the air pressure becomes great enough to escape under the rear step 4. The runners extending longitudinally of the bottom and being inclined at a planing angle to the water impart a lift to the stern, which quickly reduces water friction on the bottom towards the stern and quickly provides an opening at the stern through which air developed by frontal pressure can pass out, thus enabling the air pressure lift to be developed equally throughout the length of the hull. When speeds, approaching maximum are attained substantially the rear portion H only of the runners I are riding on the water and the remainder of the hull is supported on a body of air slightly greater than atmospheric. The rear end of the runner being in planing contact with the water surface causes the opening thus defined between the water surface and the rear step to remain constant and to allow a constant pressure to be maintained under the hull, so that the hull attains a riding angle which remains constant too, thus preventing pounding or jumping of the bows.

What I claim as my invention is:

1. A hydroplane hull having a forward and a rear step, side boards extending downwardly into the water adjacent to and below the rear step to confine the air stream passing under the hull, a pair of transversely spaced planing surfaces mounted between the lowermost levels of the rear step and in contact with the side boards, whereby said planing surfaces are adapted to plane upon the water surface and to maintain the air gap developed by the air stream blowing under the rear step substantially constant under a given hull speed.

2. A hydroplane hull having a forward and a rear step, side boards extending downwardly into the water adjacent to and below the rear step to confine the air stream passing under the hull, a pair of planing transversely spaced surfaces mounted between the lowermost levels of the rear step and in contact with the side boards, whereby said planing surfaces are adapted to plane upon the water surface and to maintain the air gap developed by the air stream fiowing under the rear step substantially constant under a given hull speed, said planing surfaces being disposed forwardly of the stern step.

3. A hydroplane hull having a forward and a rear step, side boards extending downwardly into the water adjacent to and below the rear step to confine the air stream passing under the hull, a pair of transversely spaced planing surfaces mounted between the lowermost levels of the rear step and in contact with the side boards, whereby said planing surfaces are adapted to plane upon the water surface and to maintain the air gap developed by the air stream flowing under the rear step substantially constant under a given hull speed, said planing surfaces being at a greater inclination towards the water surface than the bottom of the hull immediately forward of the rear step.

4. A hydroplane hull having a forward and a rear step, side boards extending downwardly into the water adjacent the rear step, and a runner extending longitudinally of the bottom of the hull substantially in contact with each side board, the forward end of said runners being above the level of the forward step and the rear end of the runners being below the level of the rear step.

5. A hydroplane hull having a forward and a rear step, side boards extending downwardly into the water adjacent to and below the rear step, and a runner secured to the bottom of the hull extending longitudinally of the bottom of the hull substantially in contact with each side board,

the forward end of said runners being above the level of the forward step and the rear end of the runners being below the level of the rear step, the angle of the lower face of said runner being inclined downwardly and rearwardly from the horizontal to a greater extent than the angle of the bottom of the hull between the rear and the forward step.

6. A hydroplane hull having a forward and a rear step, side boards extending downwardly into the water adjacent the rear step to confine the air stream passing under the hull, said side boards terminating at their forward ends adjacent to the rear of and above the front step.

ERNEST WILLIAMS EASTHOPE. 

